1. Field of the Invention:
This invention relates to building wall structures, and more particularly to controlled release wall structures adapted to collapse inwardly or outwardly relative to the building framework when acted upon by abnormally high positive or negative wind pressures.
2. Description of the Prior Art:
In the past, building wall structures have been adapted to be separated from the structural framework -- usually away from the framework -- when the wall structure experiences a selected elevated pressure. Such elevated pressure may be created by explosions occurring within the confines of the building or by abnormally high negative wind pressures. Such wall structures have been provided wherein the panels.
(a) are held in place by resilient members, see, for example, U.S. Pat. Nos. 3,112,535; 3,150,749; 3,258,890;
(b) are secured to the frame members by releasable fastening means of the type which will fail in shear or in tension, see, for example, U.S. Pat. Nos. 3,258,887; 3,807,106; and
(c) are secured to the structural framework by pressure release fasteners which incorporate a deformable metal washer which is forced over the fastener head during release of the panel, see, for example, U.S. Pat. No. 3,828,493.
In a recent development, a wall structure is provided which spans across at least two frame members and which is adapted to collapse (inwardly or outwardly) in the direction of and at a predetermined applied load. The wall structure includes a liner sheet having one end releasably retained to a first frame member, an outer facing sheet, and at least two subgirts disposed between and secured to the liner sheet and to the facing sheet. The failure load of the wall structure is controlled by the distance between the first frame member and the subgirt adjacent thereto. The failure load of the wall structure is regulated by controlling the force distribution in the wall structure components. See, for example, U.S. Pat. No. 3,998,016.
Transparent laminated window closures are known which, in response to excessive pressures, rupture or yield inwardly or outwardly from the original plane of the window. In one arrangement, one or both of the glass plates of the laminate may be split or scored along predetermined lines such that the closure ruptures into a selected number of segments, each segment having marginal edges hinged to the frame. See, for example, U.S. Pat. No. 2,679,467. In a second arrangement, the closure comprises triangular segments having a yieldable strip, such as elastic tape or the plastic interlayer of the laminate, which bridges across the adjacent edges of the segments. The yieldable tape flexes during application of excessive pressures, thereby allowing the triangular segments to move in the direction of the applied pressure. See, for example, U.S. Pat. No. 2,721,157.